1. Field of Invention
The present disclosure relates to power electronics technology. More particularly, the present disclosure relates to a control method for reducing audio noises.
2. Description of Related Art
Currently, as a power supply conversion device of an electronic product, a power source converter is widely applied to various fields including military industry, scientific research, industrial control, communication, electric power, LED illumination, instruments and apparatuses. Along with the continuous improvement of the power source converter, the operating efficiency of the power source converter in light load and no-load output situation is increasingly valued.
Generally, in order to improve the efficiency, when the output power of the power source converter is lower than a preset value, the power source converter enters into a Burst-Mode (hereinafter referred to as BM mode). Herein, the BM mode is also referred to as a skip cycle mode or a discontinuous operation (or burst) mode, in which the power source converter stops operating for a period of time (Tburst—off) between two continuous operating pulses (Tburst—on period). In the Tburst—on period, electrical energy is transferred from an input side to an output side of the power source converter, and an energy storage component in the power source converter stores the electrical energy. In the Tburst—off period, the electrical energy is not transferred from the input side to the output side of the power source converter, and the energy storage component in the power source converter releases the electrical energy to the output side. However, traditional magnetic components (such as inductors and transformers) of a power source converter in the BM mode are often affected by variable magnetic fields with frequency equal to that of the BM mode, and thus audio noise is caused. Once the frequency is close to the mechanical resonant frequency of the magnetic components, resonance case happens to the magnetic components, and at this time, the audio noise is especially apparent.
Currently, two technical solutions are mainly adopted for disposing of the audio noise of the magnetic components under the BM mode. One technical solution is adopted to change the mechanical structure and the installation manner of the magnetic components, such as bonding, securing, increasing of sound propagation distance and adding of a sound-proof housing, but these manners cannot fundamentally solve the audio noise problem. The other technical solution reduces the amplitude of the variable magnetic fields with frequency equal to that of the BM mode, so as to reduce the audio noise. However, these methods for reducing the amplitude of the magnetic field are often relatively mechanical and are not beneficial to optimize the efficiency of light load or non-load state.
In order to solve the above disadvantages existing in the conventional techniques, the related industries have been endeavored to seek for a solution, but an appropriate manner is not found for such a long time. Therefore, it is one of current important research and development subjects how to design a control method for reducing the audio noise so as to reduce or eliminate the audio noise when the power source converter operates under the light load or non-load state, and this is also an improvement object in urgent need by the related art.